This invention relates to granular components containing alkylaminotriazole for use in machine dishwashing detergents and to a process for its production.
Granular machine dishwashing detergents are well known because they are easy to measure out, pourable and free-flowing, stable in storage and visually attractive to the consumer.
Alkylaminotriazole is a corrosion-inhibiting component which is now widely used in detergents containing available oxygen. Unfortunately, its chemical stability in such systems is limited because alkylaminotriazole is degraded by alkaline substances. As a result, yellow-colored and pungent-smelling oxidation products are formed, above all in the event of prolonged storage, leading to discoloration of the detergent, to a loss of the corrosion-inhibiting effect and to inadequate acceptance of the product by the consumer.
GB 1,400,444 (Unilever) describes granules which contain a uniformly dispersed organic extrudable solid selected from the group of corrosion inhibitors, such as benzotriazoles, bismethylene benzotriazoles, ethoxylated phosphate esters, oximes and hydroxamates and which are suitable for incorporation in detergent powder compositions. An important feature of these granules is that the extrudable solid is selected so that the granules dissolve in water at 20.degree. C. in less than 10 minutes and preferably in 2 minutes. The described document claims all "suitable" processes which work on the mixture of the organic extrudable solid, including for example grinding, pelleting, extrusion, compaction and pressing. The document points out that, through the use of organic solids, there is generally no segregation of various particles in detergents containing the granules according to the invention.
WO 9511416 (Procter & Gamble) describes a bleaching composition suitable for machine dishwashing which contains an oxygen bleaching agent, paraffin oil and a benzotriazole component, the component as a whole being intended for use in detergents. The components may be present as powders, granules, pastes, liquids, gels, tablets, granular preparations being preferred. Densities of at least 650 g/l or, normally, of at least 700 g/l and preferably in the range from 800 to 1200 g/l and particle sizes distributed so that no more than 5% of the particles are larger than 1.4 mm in diameter and no more than 5% of the particles are smaller than 0.15 mm in diameter are preferred. The document in question describes several processes for obtaining these granules. One preferred process for the production of the compound comprises premixing paraffin oil and a dispersant, the resulting premix being sprayed onto the rest of the composition. The dispersant is advantageously a nonionic surfactant. However, another preferred process known as coating comprises spraying paraffin oil and dispersant onto the bleaching agent which reduces the dissolving rate of the bleaching agent in water. The coated bleaching particles are then dry-blended with the rest of the composition. The document in question also describes compacting of the bleaching agent before it is dry-blended with the remaining ingredients of the composition. However, it does not show how alkylaminotriazole is supposed to be uniformly incorporated in a free-flowing component of a dishwashing detergent.
U.S. Pat. No. 4,321,166 (Procter & Gamble) describes builder-free liquid detergent systems which contain a mixture of aromatic triazoles and oligomeric olefinic fatty acids as corrosion inhibitor. The corrosion inhibitor is said to prevent discoloration of the metal basket in automatic washing machines and the discoloration of fibers which come into contact with that basket. The document in question does not show how organic redox-active substances can be uniformly incorporated in bleaching components or how silver can be protected by these components.
Hitherto unpublished DE 196 31 787 describes a process for the production of a granular free-flowing component which comprises a solid (I) melting above 50.degree. C. from the group of organic redox-active substances, preferably from the group of benzotriazoles, and a constituent (II) solid at its melting temperature selected from the group of builder components typically encountered in dishwashing detergents and one or more other constituents from the group of hydrocarbon carbons or mixtures thereof and one or more other constituents from the group of polar organic solvents and surfactants, the ratio of solid (I) to solid (II) being from 1:100 to 2:1, preferably from 1:70 to 3:2 and more preferably from 1:50 to 2:3 and the component having a particle size of 0.01 to 2 millimeters, preferably from 0.05 to 1.8 millimeters and more preferably from 0.1 to 1.6 millimeters.
Hitherto unpublished DE 197 01 031 describes the use of alkylaminotriazoles as silver protectors in machine dishwashing detergents.
However, none of the patent specifications cited above shows how a granular free-flowing component containing alkylaminotriazole can be produced. The problem lies inter alia in the fact that mixtures containing alkylaminotriazole which are conventionally produced by granulation, for example using granulation liquids, are difficult to process because the mixture tends to cake and, as a result, does not flow freely. The component should retain its physical property of free flowability over a prolonged period. However, the problem of the chemical stability of components containing alkylaminotriazole also cannot be solved by the teachings of the documents cited above. This property becomes all the more important against the background of the incorporation of these components in machine dishwashing detergents. Here, the properties of physical and chemical stability of the granular components are particularly desirable. Alkylaminotriazole should remain stable in the presence of oxidative and alkaline components so that it can still act as a silver protector. Another serious problem is that, in its production process, alkylaminotriazole is obtained in the form of a solution in hydrochloric acid. If a formulation such as this is applied to an alkaline support, the alkylaminotriazole decomposes immediately.
The problem addressed by the present invention was to provide free-flowing, storage-stable homogeneous granules containing alkylaminotriazole which would be suitable for protecting silver in machine dishwashing. The alkylaminotriazole present in the granules would be protected against oxidative attack.